This lesson will quickly go over four heart valves, their location, what can go wrong with them, and then two detailed examples of how their dysfunction affects the body.
When Heart Valves Fail
The valves in your heart, just like valves in a plumbing system, are there to help control and regulate the flow of a liquid. In the case of the body, that would be the blood.Without valves, this important control of blood flow would be impossible and would actually result in heart failure.
Unfortunately, there’s a predicament some people face. Their valves can malfunction, and this can end up causing heart failure, too. So we’ll discuss the two big problems that occur in heart valves.
Valve Locations and Names
Venous (deoxygenated) blood enters your right atrium and moves through the tricuspid valve and into the right ventricle. The tricuspid valve is the heart valve that separates the right atrium from the right ventricle.
From there, blood flows through the pulmonary valve, the valve that separates the right ventricle from the pulmonary artery, and then into the lungs.The blood leaves the lungs and enters the left atrium and passes through the mitral valve, the valve that separates the left atrium from the left ventricle. Once in the left ventricle, the blood is ejected through the aortic valve, the valve that separates the left ventricle from the aorta, and then it goes out into general circulation from there.
One of the problems that can affect any of these four valves is known as valvular stenosis, a condition that results in narrowed and hardened valves.What this means is that blood flowing from one structure in your heart to a downstream structure separated by a stenotic valve has a very hard time moving along. Think about hooking up a water hose in your backyard and turning on the water.
The water will flow just fine. But if you pinch or squeeze one area in the hose, the water will not be able to make it downstream nearly as well, and the hose will begin to bulge in the area preceding the constricted area, the upstream area.Similarly, when there is a stenotic valve, the chamber of the heart preceding the valve enlarges as a result of increases in volume or pressure.
Let’s work on one specific example. Let’s say the mitral valve is stenotic. This means that the left atrium has a hard time pushing blood into the left ventricle because the mitral valve becomes narrowed and hardened.
This causes blood to back up in the left atrium, which results in its dilation. This causes an even more serious upstream effect. Upstream from the left atrium is the pulmonary vasculature. Increased amounts of backed up blood here results in pulmonary hypertension (increased blood pressure). Pulmonary hypertension can cause leakage of fluids into the lungs themselves, causing difficulty breathing and impairing oxygenation of the blood.Pulmonary hypertension also means that even further upstream from the lungs, the right ventricle has a much harder time pumping blood into the lungs.
This means people with mitral valve stenosis may develop right-sided heart failure due to an overworked right ventricle.Going back to our example with the hose, here the hose dilates upstream to the place where you pinch. This causes water to back up in the pipes inside the house, resulting in increased pressure in those pipes. This means water begins leaking out of the pipes and into your basement to try and relieve this increase in pressure. This increased pressure inside of your house’s pipes also means the city water plant has a much harder time pushing water into your house’s water pipes.
This can overload the machinery that pumps this water, resulting in their failure. I exaggerated there, as you know, but at least you get the picture.The reason I used the mitral valve as an example is because it demonstrates how one little defect causes a whole sequences of events related to the heart and lungs. It’s not just the mitral valve or left atrium that’s affected in mitral valve stenosis.
One other thing mitral valve stenosis can lead to is tricuspid valve regurgitation. Valvular regurgitation refers to a valve that allows for the backflow of blood – meaning, our valves that I talked about before are supposed to be one-way valves only. They are supposed to allow forward flow of blood but should seal tightly to prevent backward flow of blood. If the blood flows in a retrograde fashion, we term this ‘regurgitation.’Let’s think about what this can cause inside of the heart. Let’s pick the aortic valve in this example.
During aortic regurgitation, blood flows back from the aorta and into the left ventricle. This causes the amount of blood (volume) to increase and its pressure to rise in the left ventricle. This causes the left ventricle to work harder and harder, resulting in left ventricular hypertrophy, or an increase in the thickness of the ventricular muscular wall. This can eventually result in heart failure.
Furthermore, a collapsing (or water-hammer) pulse may be noted during aortic regurgitation. What this means is that the pulse is strong for a moment but quickly disappears. This is because as the left ventricle ejects the blood into the aorta, the pulse pressure increases, but because the blood quickly flows back from the aorta and into the left ventricle, the pressure cannot be maintained in the arteries for long, leading to a collapsing pulse.
So, if our city water plant is sending water to our home through a series of valves, but the valves allow for the backflow of water, the water pressure in our house will be strong only when the water plant actively pumps the blood forward. But as the water pump momentarily stops before the next forward pump, the valves allow for the backflow of water, leading to a collapse in water pressure at home.Regurgitation can also damage the inner lining of the heart, the endocardium. I like to think of the stream of blood regurgitating back from a ventricle into an atrium as a jet stream of blood.
As the ventricle contracts to push blood forward, blood shoots back into its respective atrium due to valvular regurgitation. This jet stream of blood, like a giant fountain stream, is very powerful and slams the atrial endocardium with a lot of force. This damages the endocardium, leading to jet lesions, which are little scars in the endocardium.Regardless of which valve causes which problem, diagnosis involves listening for specific heart murmurs and looking at the heart via an echocardiogram. Treatment for valvular issues is many times performed via surgical correction, especially in serious cases.
The four valves that are affected by valvular stenosis, a condition that results in narrowed and hardened valves, and valvular regurgitation, which refers to a valve that allows for the backflow of blood, include:
- The tricuspid valve, which is the heart valve that separates the right atrium from the right ventricle.
- The pulmonary valve, the valve that separates the right ventricle from the pulmonary artery.
- The mitral valve, the valve that separates the left atrium from the left ventricle.
- The aortic valve, the valve that separates the left ventricle from the aorta.
Depending on which of the two problems affects which valve, downstream and upstream consequences will occur in every case, oftentimes resulting in the need for surgical correction of the valves.
After completing this lesson, you should be able to:
- Identify the four valves of the heart
- Recognize the causes of valvular stenosis
- Understand the backflow condition of valvular regurgitation